The largest one-day percentage loss recorded by the S&P 500 during the 2020 COVID-19 crash was 12.0% on March 16, 2020.
The decline came as the COVID-19 pandemic spread globally, governments imposed restrictions, and investors reassessed economic activity, corporate earnings, and financial risk. The S&P 500 fell 12.0% in one session, its worst single-day percentage decline since the 1987 crash.
Trading was halted temporarily several times during the broader sell-off because market-wide circuit breakers were triggered. The rapid decline pushed the index into a bear market, commonly defined as a fall of at least 20% from a recent high.
The 2020 crash was unusually fast: U.S. stocks moved from a record high to a bear market in weeks. Massive fiscal support, central-bank actions, and improving expectations later produced a powerful rebound, although the economic and public-health effects remained significant.